The present invention relates generally to connection devices for joining together pre-cast concrete members such as panels or columns stacked one on top of the other to form building walls, the connection devices employing a grouted connection between a block-out tube cast into the top of a lower concrete member and a structural rod cast into the bottom of an upper concrete member. More particularly, the present invention relates to an ovalized block-out tube that provides structural strength, in addition to a tolerance for misalignment with the structural rod, when the upper panel is assembled onto the lower panel.
Conventional connections for joining cast concrete wall panels use metal spiral tube sections cast into the top of the lower panel. These block-out tube sections are mounted on a framing member in the form used to cast the panel, oriented inwardly in the center of the top wall of the panel. Tape is used to close the bottom of the spiral tube sections. After pouring of the concrete panel and setting of the concrete, the forms are removed and the open ends of the tubes are sealed or taped, or alternatively a plug is driven into each tube.
A lower panel with conventional spiral tubes cast in place is erected and the tubes are opened and filled with grout or mortar. An upper panel with structural rods aligned with the tubes and extending downwardly from the lower surface of the panel is lowered onto shims with the rods extending into the grout placed in the opened tubes. The grout sets to form a joint between the two panels.
It is difficult to secure the spiral tube used in the conventional joint to the forms used for pouring a lower panel. The taped seal at the inner end of the tube may leak allowing concrete to flow into the interior of the tube during the casting of the lower panel. The tape and plug seals used to close the tube sections are ineffective and frequently allow water, moisture, and dirt to collect in the tubes prior to the erection of the panels. If the water in the tube freezes there is a risk that resultant expansion will crack and ruin the panel. Any debris collected within the tube will degrade the quality of the connection formed by the mortar when the panels are erected. The sharp corner in the concrete at the bottom of the tube concentrates stress in the cast panel and can lead to cracking of the panel.
In addition, the circular cross-section of the spiral tubes is not much larger in diameter than the structural rods which are mortared therein, and thus do not allow any appreciable tolerance for misalignment of the respective connection devices of the two panels. Often concrete panels are joined by multiple sets of tubes, spaced along the length of top surface of the lower panel, and rods, spaced along the bottom surface of the upper panel. If there is slight variation in the spacing of the tubes as compared with the spacing of the rods, assembly of the two panels becomes very difficult if not impossible.
An improvement to the conventional connection apparatus is disclosed in U.S. Pat. No. 5,134,828 [Baur] that discloses a closed-end blow molded tube for use as the block-out in a pre-cast lower panel. While this device overcomes some of the problems existing in the conventional connection device as described previously, it leaves some disadvantages unaddressed and further introduces new disadvantages. This device nicely solves the problem of keeping water, moisture, and debris from entering the block-out tube before, during, and after pouring of the concrete panel. However, this device is nominally circular in cross-section and straight-sided along its length, and therefore includes a series of recesses to engage the surrounding concrete and the internal grout. Engagement of the tube recesses with the concrete and the grout gives the device the structural strength important for joining the lower panel to an upper panel, but also creates areas of stress concentration in the pre-cast concrete panel that may increase the tendency of the concrete panel to crack. Additionally, the circular cross-section is the same as that used in the conventional spiral tube and therefore does not provide for any additional tolerance for misalignment of tubes and rods along the length of the two mating concrete panels. As a further minor inconvenience, this device is nailed to the concrete pouring forms and when the forms are removed, the nails are left sticking outwardly from the concrete panel with the nail heads trapped between the tube mounting flange and the concrete.
Accordingly, it is an object of the present invention to provide a block-out tube for use in joining pre-cast vertical concrete panels that provides structural strength without introducing stress concentrations into the poured concrete or grout. It is another object of the present invention to provide a block-out tube that prevents the entry of water, moisture, or debris that could degrade the quality of the grout connection inside the tube.
It is yet another object of the present invention to provide a block-out tube which may be separated from the concrete pouring form without leaving exposed nails protruding from the finished concrete panel. It is a further object of the present invention to provide a block-out tube which accommodates for minor misalignments of spacing and positioning between the tubes along the length of the lower concrete panel into which the tubes are cast and the structural rods along the length of the mating upper concrete panel into which the rods are cast.
Other objects will appear hereinafter.